The younger man appeared in court today and was due to reappear on Thursday, while the 29-year-old will make his first court appearance on Monday.
Mr Hercock said information from witnesses had led police to believe a fight had preceded the stabbing.
"We believe that prior to Mr Valentine's death there was some type of altercation involving a number of other people," he said.
"We do not believe that this was a random attack. We understand that there was disagreement in regards to some minor matters between the victim and those arrested."
Mr Hercock said police were not looking for anyone else in relation to the death.
Police were now seeking sightings of a white Mitsubishi Pajero 4WD, registration CTJ418, between 6pm to midnight yesterday.
"We believe this vehicle has been used at some point prior to, and after the fatal stabbing of Mr Valentine," Mr Hercock said.
"Even though we have made arrests, this investigation is still ongoing and we are appealing to the public for sightings of the vehicle mentioned above and for any information relevant to this investigation.
"Please come forward and contact us if you know something."
A scene examination was expected to continue over the next two days, while a post-mortem examination will be conducted tomorrow.
Police said their thoughts and condolences were with Mr Valentine's family and friends at this difficult time.
